Over the years, engineers have come to recognize that undesirable emissions can be reduced, and performance improved, across most of an engine's operating range by making each fuel injection event begin relatively slowly and end as abruptly as possible. This type of injection mass flow rate profile is more commonly referred to in the art as rate shaping. It is well known that there have been a wide variety of devices and schemes proposed for producing desired fuel injection rate shapes for as many different fuel injectors. Unfortunately, many of these proposals are too complex for realistic mass production or too difficult to manufacture in a way that produces consistent reliable results. Others improve a front end rate shape by sacrificing on an abrupt end to injection, or vice versa.
The present invention is directed to these and other problems associated with the production of desired rate shapes in fuel injectors.